Blow molding machines that use clam shell-type mold apparatus to form the upper portion of a blow mold cavity and a cooperating bottom mold portion to complete the cavity are well known in the art. See, for example, U.S. Pat. No. 5,968,560 relating to a blow molding device for producing thermoplastic containers; U.S. Pat. No. 6,447,281 relating to a blow mold shell and shell holder assembly for a blow-molding machine; and U.S. Pat. No. 5,326,250 relating to opening and closing mechanism for a portfolio blow and blow-stretch mold.
Machines of this type operate at high speeds to maximize production throughput. As the opposing clam shell halves of the mold apparatus swing closed at the blow station during each blow cycle, push-up mechanism at the station below the clam shell halves must elevate a bottom portion of the mold up into proper position between the clam shell halves just before they close. Once closed, the clam shell halves grip and retain the bottom blow mold portion against separation from the rest of the mold during the high pressure blow cycle. Lock ring halves carried on the upper mold halves match up with complemental structure on a ring carried on the push up mechanism to retain the push up mechanism and thus the bottom mold portion in place when the upper mold halves fully close.
Obviously, the timing between the upper mold halves and the push-up mechanism is critical. If the timing is imperfect for any reason, the mold halves may close too soon and the mold surfaces of the bottom mold portion may be damaged by the lock ring segments as they prematurely enter the path of travel of the upwardly moving bottom mold portion.
The present invention provides a lock up arrangement in which the lock ring segments on the upper mold halves are configured to avoid encroachment into the path of travel of the lower mold portion even when the timing is imperfect between the upper mold halves and the push-up mechanism. A bottom mold portion that might be damaged by out-of-time lock ring segments of conventional design will be spared damage by the inventive segments due to the fact that they are configured to always remain out of the path of travel of the bottom mold portion even if the upper mold halves close prematurely.
To this end, the present invention contemplates lock ring segments that are bolted to the bottom edge of upper mold halves as in the past. However, instead of the prior art approach wherein an inwardly projecting annular ledge on the segments protrudes into the path of travel of the bottom mold portion, the new lock ring segments are each provided with one or more outwardly recessed notches that present ledges located outside the profile of the bottom mold portion when the mold halves are closed. In turn, one or more outwardly projecting lugs on the ring that supports the bottom mold portion are configured to slip into the notches of the lock ring segments and onto the support ledges thereof when the mold halves close about the bottom mold portion and push-up mechanism. The lugs of the support ring are thus prevented by the ledges from moving away from the upper mold portion. The notches and their ledges are located between respective pairs of bolt locations on the lock ring segments.